Stiff Brake Pedal After Sitting

Cracker_Box

Well-Known Member
First Name
Blake
Joined
Jun 1, 2019
Messages
65
Reaction score
122
Location
Lafayette, LA
Vehicle(s)
2019 Wrangler Sport S
The vacuum for the booster is supplied by an electric vacuum pump that sits below/under the alternator, being that this setup is not typical for most N/A engine vehicles it is very well possible that the vacuum system isn't design to hold for long once the ignition is switched off. Which would cause the stuff pedal.

I'm a tech for Audi we have similar stuff on our diesel engines and I've noticed it with them before on occasion.
Advertisement

 

Bigtuna33

Member
Joined
Jul 26, 2019
Messages
8
Reaction score
6
Location
Wisconsin
Vehicle(s)
JLUR
The vacuum for the booster is supplied by an electric vacuum pump that sits below/under the alternator, being that this setup is not typical for most N/A engine vehicles it is very well possible that the vacuum system isn't design to hold for long once the ignition is switched off. Which would cause the stuff pedal.

I'm a tech for Audi we have similar stuff on our diesel engines and I've noticed it with them before on occasion.
Makes sense; is there a solution or just have to live with it?
 

tobyw

Well-Known Member
First Name
Toby
Joined
Mar 26, 2018
Messages
114
Reaction score
207
Location
Washington
Vehicle(s)
2018 JLU-R
Mine just started doing this Sunday morning... ~9,500 miles and never had the issue before, but both starts since Sunday morning have required massive brake pedal pressure before the push button would recognize anything and allow it to start?? It makes me wonder if there is a check valve or something in the system between the vacuum pump and the booster that is failing and allowing the vacuum to release rather than being stored in the system for startup?
 

The Fixer

Well-Known Member
First Name
Steve
Joined
Aug 7, 2019
Messages
407
Reaction score
353
Location
North Jersey
Vehicle(s)
2018 Mojito! JLS, 2018 Firecracker JLUSS
Build Thread
Link
Occupation
Teacher
My wife's JLUS has this happen on occasion. We've had it since May '18 and put 12K miles on it. My JLS has not had this happen yet; got mine in July '19 and have ~3500 miles on it.
 

Mlentz

New Member
First Name
Maggie
Joined
Jan 24, 2020
Messages
1
Reaction score
0
Location
Florida
Vehicle(s)
2020 Jeep Wrangler Sport
It doesn't appear that anyone has reported this issue on the forum...wondering if it's only me? For the last 3 weeks, when I get into the Jeep after it's been sitting a few hours, the brake pedal is VERY stiff. It's like you pumped it while the car was off is the only way I can describe it. As soon as it start up, all is fine. I have 4000 miles on it and it just started happening. Its clockwork the last 3 weeks and when my service appointment finally came OF COURSE the damn thing was fine (so they reported). I did go over and check it myself because they claimed they were driving it and I made clear the issue can be noticed only before startup. I made mention that my very limited research pointed to the brake booster or a vacuum leak but that's just a guess from my Google searches. So, needless to say, I got the car home and it immediately behaved abnormally BUT it did have a couple instances where it worked as expected. So not sure - these intermittent things make me crazy. Tonight when I pulled it into the garage, I notice that after I depressed the brake and let off - there was a strange noise for about 15-20 seconds. Not sure what that was but it seems to be reproducible so if nothing else I'll bring it back this week and ask what that noise is because I never heard that before. Anyone have thoughts on what this could be? THANKS MUCH!
This happened to me last night. I went to start my car after only about 20min of it sitting. I couldn’t press down on the pedal all the way. After 15min of me trying to start it, I pushed down all the way and felt like I was braking the pedal. Finally it started and I took it straight home and had it towed to the dealership. It’s a brand new 2020 Wrangler with 4000 miles and Iv already had to take into the shop once. Of course they called me today and said they couldn’t find anything wrong with it. I know once I pick it up, it will act up again. If anyone has figured out why it’s happening and/or if it’s stopped please let me know! Scared to drive it now!
 

1quick1

Moderator
Staff member
Moderator
Joined
Oct 16, 2017
Messages
1,559
Reaction score
1,889
Location
Colorado
Vehicle(s)
2018 JLUS
Vehicle Showcase
1
This happened to me last night. I went to start my car after only about 20min of it sitting. I couldn’t press down on the pedal all the way. After 15min of me trying to start it, I pushed down all the way and felt like I was braking the pedal. Finally it started and I took it straight home and had it towed to the dealership. It’s a brand new 2020 Wrangler with 4000 miles and Iv already had to take into the shop once. Of course they called me today and said they couldn’t find anything wrong with it. I know once I pick it up, it will act up again. If anyone has figured out why it’s happening and/or if it’s stopped please let me know! Scared to drive it now!
You won't break the pedal. I was one of the first people to report this and find the workaround. It works 100% the time if I give it a firm push. It seems that it takes a certain amount of effort to trip the signal that the pedal is in fact pushed in. Annoying but don't bother with the dealer. I've never mentioned it because if you don't have something glaring like a piston physically sticking out of the hood they won't be able to reproduce it.
 
OP
OP

bbradshaw14

Well-Known Member
First Name
Brian
Joined
Jan 21, 2018
Messages
51
Reaction score
64
Location
Wisconsin
Vehicle(s)
2018 JLU Sahara
Occupation
Global Project Manager
This happened to me last night. I went to start my car after only about 20min of it sitting. I couldn’t press down on the pedal all the way. After 15min of me trying to start it, I pushed down all the way and felt like I was braking the pedal. Finally it started and I took it straight home and had it towed to the dealership. It’s a brand new 2020 Wrangler with 4000 miles and Iv already had to take into the shop once. Of course they called me today and said they couldn’t find anything wrong with it. I know once I pick it up, it will act up again. If anyone has figured out why it’s happening and/or if it’s stopped please let me know! Scared to drive it now!
I have 22,000 miles now and the issues comes and goes. Nothing major to report and the dealer either is or pretends to be clueless. I’ve always been able to get it to start by pressing harder than. Normal when it happens so have lived with it. A little annoying for a $52,000 vehicle but won’t stop me from getting another one in a year and a half. Good luck!
 

carpendj

Member
Joined
Jan 15, 2021
Messages
18
Reaction score
13
Location
Austin, TX
Vehicle(s)
2020 Jeep Wrangler Unlimited, 2019 GMC Sierra AT4
I have the same problem on most days. 2020 Wrangler Unlimited Willys - 3.6 Auto with ESS. Purchased new in August 2020 and I have only covered around 1700 miles. I park the jeep in my garage overnight. I got into it one morning and noted that the brake pedal was super stiff. Hardly any movement at all. Tried to start it and it would not start. If you want to experience it for yourself, simply try to start your jeep without touching the brake pedal. I was about to get it towed but somehow had a hunch to push down on the brake pedal as hard as I could. It then started. I have taken it to the dealer twice and they cannot find any problems. They even kept it overnight and of course, it did not fail for them the next morning. They gave me a loaner Gladiator and it even happened to me once in that. Gladiator was parked on my driveway overnight and it started no problem. Drove to a coffee shop, went in and grabbed a coffee, came out and the brake pedal was stiff and it would not start. Seems to me that there is some issue here and either Jeep are not aware of it or they have not yet found a solution. I have found that you either have to push the pedal down real hard OR you can use the remote start function on your keyfob if you have that option. I tried scanning for codes myself and came back with nothing wrong. My jeep dealer says that they cannot contact Jeep technical support because they have not seen the issue and my Jeep is not reporting any issues. Its very frustrating to be honest. I am keeping on eye on this forum hoping that someone finds a solution.
 

Capricorn

Well-Known Member
Joined
Apr 1, 2018
Messages
444
Reaction score
205
Location
Las Vegas, NV
Vehicle(s)
Jeep Wrangler JL Willys Unlimited 2021 3.0L EcoD, Dodge Durango R/T 2019
Occupation
Network Architect & Engineer
Probably battery related?
 
OP
OP

bbradshaw14

Well-Known Member
First Name
Brian
Joined
Jan 21, 2018
Messages
51
Reaction score
64
Location
Wisconsin
Vehicle(s)
2018 JLU Sahara
Occupation
Global Project Manager
I have the same problem on most days. 2020 Wrangler Unlimited Willys - 3.6 Auto with ESS. Purchased new in August 2020 and I have only covered around 1700 miles. I park the jeep in my garage overnight. I got into it one morning and noted that the brake pedal was super stiff. Hardly any movement at all. Tried to start it and it would not start. If you want to experience it for yourself, simply try to start your jeep without touching the brake pedal. I was about to get it towed but somehow had a hunch to push down on the brake pedal as hard as I could. It then started. I have taken it to the dealer twice and they cannot find any problems. They even kept it overnight and of course, it did not fail for them the next morning. They gave me a loaner Gladiator and it even happened to me once in that. Gladiator was parked on my driveway overnight and it started no problem. Drove to a coffee shop, went in and grabbed a coffee, came out and the brake pedal was stiff and it would not start. Seems to me that there is some issue here and either Jeep are not aware of it or they have not yet found a solution. I have found that you either have to push the pedal down real hard OR you can use the remote start function on your keyfob if you have that option. I tried scanning for codes myself and came back with nothing wrong. My jeep dealer says that they cannot contact Jeep technical support because they have not seen the issue and my Jeep is not reporting any issues. Its very frustrating to be honest. I am keeping on eye on this forum hoping that someone finds a solution.
Nothing was ever found on mine but I will say that over the years it happened less and less. I traded it in on Dec 19th for a 2021 so that solved it for me. Earlier in this thread someone mentioned this being related to the vacuum system and I believe they are right on. Here is additional info I found in a Google search.

https://techtalk.mpbrakes.com/how-to-series/how-to-diagnosing-a-hard-brake-pedal

Nothing ever happened as a result of this - never a braking issue, indicator light, or anything else but sure was annoying. Good Luck!
 
Advertisement

Motor City Aftermarket
 
Advertisement
Top